FIG. 1 schematically illustrates the general construction of a prior art electromagnetic railgun. The railgun includes a pair of rails 12 and 14 that typically comprise a pair of metal plates positioned parallel to and spaced apart from one another. Rails 12 and 14 form barrel 16 that includes breech end 18 and muzzle end 20. Armature 22 is sized so as to slide between rails 12 and 14. The armature may be part or all of the projectile that is fired by the railgun. Rails 12 and 14 are connected to capacitor 24 via lines 26 and 28 and switch 30.
In one type of railgun, armature 22 is electrically conductive, and makes sliding electrical contact with rails 12 and 14. When switch 30 is closed with the armature at breech end 18, current begins to flow between the rails through the armature, the current path through the armature being designated by reference numeral 32. This current produces a magnetic field to the left of the armature, and directed into the plane of the drawing. This magnetic field interacts with the current flowing through the armature via path 32, to create an electromagnetic force that causes the armature to accelerate to the right along barrel 16, and out of muzzle end 20 of the railgun. In a second type of railgun, known as a plasma armature railgun, current flows along path 34 through a plasma created by the electrical field between the rails to the left of an electrically insulating projectile which is used in place of the armature. Current through the plasma interacts with the magnetic field generated by the current in the rails and results in acceleration of the plasma, and therefore of the insulating projectile, to the right along barrel 16.
In a distributed energy store railgun, the energy sources, e.g., the capacitors, switches, and connecting lines, are distributed along the length of the barrel, as opposed to at the breech end of the barrel. All capacitors are precharged, and are sequentially discharged in timed relationship to one another when the railgun is fired. In particular, the switch associated with each capacitor is closed as the armature passes the point at which the connecting lines from that capacitor feed electrical current into the rails. Current fed in before the armature reaches this point must be avoided, since it will tend to accelerate the armature in the wrong direction. Because of the requirement for precise timing of the discharges of the different energy sources, relatively complex control circuits are necessary for reliable operation of conventional distributed energy store railguns.